1. Field of the Invention
This invention is concerned with an improved process for the manufacture of hydrocarbons from lower alcohols or their ethers. It is particularly concerned with the catalytic conversion of such alcohols and ethers to hydrocarbon mixtures rich in ethylene. In another aspect, this invention is concerned with a process which utilizes a catalyst composite of antimony oxide and a crystalline aluminosilicate zeolite, which composite is especially effective for the conversion of lower alcohols to ethylene and aromatic hydrocarbons.
2. Description of Prior Art
A remarkable growth in the production of synthetic fibers, plastics and rubber has taken place in recent decades. This growth, to a very large extent, has been supported and encouraged by an expanding supply of inexpensive petrochemical raw materials such as ethylene, benzene, toluene, and xylenes. Side by side with this remarkable development, there has been an increasing demand for aromatic hydrocarbons for use as high octane gasoline components. Environmental factors which limit the lead content of gasoline are likely to aggravate the need for aromatics.
Burgeoning demand for olefins, particularly ethylene, and for aromatic hydrocarbons, has of course led to periods of shortage, either due to short supply of suitable feedstocks or to limited processing capacity. In any case, it would appear desirable to provide efficient means for converting raw materials other than petroleum to olefins and aromatic hydrocarbons.
U.S. Pat. No. 3,972,832 discloses a catalyst comprising a crystalline aluminosilicate zeolite having a silica to alumina ratio of at least about 12, a constraint index of about 1 to 12, and containing phosphorus incorporated with the crystal structure thereof in an amount of at least about 0.78 percent by weight and discloses the conversion of aliphatic compounds, particularly hydrocarbons, both paraffins and olefins, by contact with the catalyst.
U.S. Pat. No. 3,911,041 describes the conversion of methanol and of dimethyl ether to hydrocarbons when contacted with phosphorous-modified ZSM-5 type catalyst.
U.S. Pat. No. 3,906,054 discloses a process for the alkylation of olefins employing as a catalyst, a crystalline aluminosilicate zeolite having a silica to alumina ratio of at least about 12, a constraint index of about 1 to 12, and containing phosphorus incorporated with the crystal structure thereof in an amount of at least about 0.78 percent by weight.
U.S. Pat. Nos. 3,894,106, 3,894,107 and 3,907,915, respectively, disclose the conversion of alcohols and/or ethers and/or carbonyls to higher carbon number hydrocarbons by contact with a catalyst comprising a crystalline aluminosilicate zeolite having a silica to alumina ratio of at least about 12 and a constraint index of about 1 to 12.
The conversion of methanol and dimethyl ether to hydrocarbons is described in U.S. Pat. No. 3,911,041.
A process for preparing attrition-resistant solid catalysts containing antimony oxide is described in U.S. Pat. No. 3,686,138, issued Aug. 22, 1972.
U.S. Pat. No. 3,979,472 describes the conversion of lower monohydric alcohols having up to four carbon atoms, their ether derivatives, or mixtures of any of these, by contact with a novel catalyst to form hydrocarbon mixtures rich in light olefins, especially ethylene, and aromatic hydrocarbons. The novel catalyst utilized in that invention is a composite of antimony oxide and a porous inorganic oxide preferably of the crystalline aluminosilicate zeolite type. The entire contents of U.S. Pat. No. 3,979,472 are incorporated herein by reference.
We now find that when a fixed bed of catalyst composite of an oxide of antimony and a crystalline aluminosilicate zeolite is utilized for a protracted period of time in converting a lower alcohol feed to hydrocarbons, as described in U.S. Pat. No. 3,979,472, a portion of the antimony component is eluted from the catalyst composite and appears downstream of the catalyst reactor. This elution effect is undesirable in that it is likely ultimately to adversely affect the selectivity of the catalyst composite, and the eluted antimony may, in addition, give rise to contamination of equipment and products.